Two Stage AP Motor????

I am well into the construction stage of my Cosmodrome Rocketry “Aerobee-Hi”. I have the electronics for the sustainer ignition and I have a system worked out for mounting it and routing the wires etc.

I’m including an altimeter in the nose cone/payload bay for deploying the parachute so I don’t have to rely on the motor, as it is always possible it might not light. As a side benefit of not using motor deployment I don’t have to duct the ejection gases around the lower electronics bay where the staging timer/battery is located.

I included a 38mm motor tube in the booster but retained the 29mm tube for the sustainer, whose length will allow for an AeroTech 180 case or others of equivalent length.

So to make a long story short, I know; too late for that, my question is; what is the most reliable low current “Igniter” I can get my hands on and what is the easiest motor brand/propellant type to ignite?

I have heard that CTI has its own BP charge to aid in ignition and actually uses a low current E-match style igniter.

What technique/s can I use that would increase the odds of sustainer motor ignition?

FYI; in this rocket the staging electronics is housed above the sustainer motor; my idea is to have the booster air-drag separate at booster motor burnout.

CTI's are the easiest to ignite. Attach a small piece of either Thermalite, Blue Thunder Propellant, or Thermite to your igniter in the upper stage.

The motor will not hesitate to light.

I am no expert, but I have lit an AP motor with a dual-deployment e-match without issues. It was late in the day, last launch, and I burned my copperhead. I was using an AT SU G80. Our vendor had already packed up, so I grabbed one of my DD e-matches and shoved it in there and hoped it would work. It did.

I think I was using one of Crazy Jim's, or something very similar.

Is “Thermolite” something you can purchase?
What exactly is it?
Doesn’t sound like something I want laying around the house. . .watching the tele all day and drinking all my beer.

What motors are available in CTI that correspond to an AeroTech 29/180 case?

Well if a Crazy Jim’s E-matches can ignite a motor then I’m in Hog Heaven.

I have me a bunch of them and the staging timer I have fires them with alacrity and just a tad of violence.

I was using the timer in “Test mode” with the CJ E-match housed in a spent Estes “D” motor casing.
It blew sparks and other burning crap a couple of feet out the open end. For a moment I thought it had lit the casing on fire.

The only problem I might have with CJ’s product is that I don’t think it will fit through the nozzle or the slot of AeroTech’s Hobbyline reloadable motors.

The “Aerobee Hi” being a fairly lightweight rocket it was my intent to fly it first using said motors.

That being said. .?. .written; all things are open to change.

Use a CTI motor in the upper stage, it has a BP pellet pressed in the top grain and the "lighter" that comes with it, is low current like mine. Do NOT augment it with anything thing else or you run the risk of over-pressurizing the motor & bad things can happen.

So simply using a CTI 29 motor as it comes will solve your problem. They will light with any timer or staging altimeter out there I know of.


Thermalite is a fuse that was used in the mining industry for explosives. Not made any more & very hard to find. You could start it with electricity or regular match/lighter.

boomtube-mk2 said:

my idea is to have the booster air-drag separate at booster motor burnout.

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The booster BT diameter is smaller than the sustainer. The booster doesn't (as I've seen) separate at burn-out. It will separate when the sustainer lights. Make sure to epoxy the inside of the booster coupler and top of the bulkhead. A thin glass cloth would be even better.

Do you mean Thermalite?
It's basically fuse but, you need an explosives permit to buy / use it.
Not sure if it's even produced any longer???

I doubt that they would have it in the UK.....


JD

boomtube-mk2 said:

Is “Thermolite” something you can purchase?
What exactly is it?
Doesn’t sound like something I want laying around the house. . .watching the tele all day and drinking all my beer.

What motors are available in CTI that correspond to an AeroTech 29/180 case?

Click to expand...

JDcluster said:

Do you mean Thermalite?
It's basically fuse but, you need an explosives permit to buy / use it.
Not sure if it's even produced any longer???



JD

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You are thinking of THERMITE.

NO!
Thermalite use to be the only way to ignite clusters, way before electronics came along;
Long before you could even walk.....


JD

blackbrandt said:

You are thinking of THERMITE.

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Thermite and Thermalite are two different things and, yes, thermalite is difficult to obtain.

Wow. Funny. I have an entire wad of thermalite fuse...

Everybody is telling me that CTI is the way to go for the sustainer motor, which $&^KS because I don’t have any CTI cases and I’m not looking to branch out into yet another motor brand/type having just entered the Loki realm of motors.

The booster BT diameter is smaller than the sustainer. The booster doesn't (as I've seen) separate at burn-out. It will separate when the sustainer lights. Make sure to epoxy the inside of the booster coupler and top of the bulkhead. A thin glass cloth would be even better.

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So even with those enormous fins dragging behind the upper stage it won’t drag off the bottom?

I’m sure I’ve seen a video of that rocket wherein it did drag separate before the sustainer fired. I hope I can get it to do that as I’d really like to not have it hanging off the back of the rocket should the sustainer motor not fire.

Three seconds after that the booster motor deploys its parachute and that can’t be a good thing if it is still attached to the upper stage. Especially since the altimeter will shortly thereafter deploy the chute for the upper stage.

That’s a lot of chutes happening altogether too close to one another.

Thanks for the tip of “glassing” the inside of the inter-stage coupler.

CTI 29mm cases are not very expensive = $24 for a 3 grain case and $18 for the rear closure. Then there's the delay drilling tool. $50 for the 29mm starter set is a great deal (3 grain case, two spacers so you can also use 1 and 2 grain loads, rear closure and delay tool). These prices are from Animal Works. I haven't surveyed other vendors for prices.

Just an occasional but satisfied customer.

You don't have to use CTI...it's not the only thing that works. AT isn't hard to airstart if you do it right...it's not some un-doable, mysterious thing. Also, DO NOT use a bare e-match to light upper stages or clusters, except for CTI motors which are set up to use them. Yes, you can get it to work sometimes, just like Q2G2s will sometimes light composites, but they aren't reliable enough on their own. Notice the account given above--it was a Blue Thunder motor, an easy to light propellant.

On that note, easy to light propellants are: AT Blue Thunder, New Blue Thunder, Warp 9, Fast Jack, Dark Matter; anything CTI with the igniter pellet.

Igniter ideas for non-CTI:

For your 29/180 or other HPR motors:

-a CJ e-match dipped in pyrogen like Magnelite, ClusterFire or Quickburst Quick Dip

For Hobbyline AND HPR motors:

-Buy Rocketflite MF wires and dip in their ClusterFire pyrogen. GROUND TEST WITH ELECTRONICS FIRST...MY PET2 TIMER WILL ONLY FIRE ONE OF THESE AS THEY ARE STILL HIGHER CURRENT THAN E-MATCHES.

-Buy Rocketflite MF wires, MagFire Pyrogen and Magnelite pyrogen. Do a small "primer" dip in the MagFire (but NOT SEALANT), let dry and do a healthy dip in Magnelite pyrogen. I haven't tested these yet but Greg Dyben, Rocketflite owner, indicated that some folks have had luck with this method and it makes much lower current, similar current requirement to e-matches.

For Hobbyline only:

-Q2G2 dipped in pyrogen of your choice...if you can find them. When the new ones come out I'd ground test first.

**FOR ALL OF THESE METHODS SCUFFING AND PAINTING THE TOP GRAIN WITH PYROGEN IS HIGHLY RECCOMENDED.**

blackbrandt said:

Wow. Funny. I have an entire wad of thermalite fuse...

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If it ain't too dried up and you aren't using it I'll buy it off you.

boomtube-mk2 said:

So even with those enormous fins dragging behind the upper stage it won’t drag off the bottom?

I’m sure I’ve seen a video of that rocket wherein it did drag separate before the sustainer fired. I hope I can get it to do that as I’d really like to not have it hanging off the back of the rocket should the sustainer motor not fire.

Three seconds after that the booster motor deploys its parachute and that can’t be a good thing if it is still attached to the upper stage. Especially since the altimeter will shortly thereafter deploy the chute for the upper stage.

That’s a lot of chutes happening altogether too close to one another.

Thanks for the tip of “glassing” the inside of the inter-stage coupler.

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No, With a bigger diameter BT, the sustainer will decelerate faster than the booster. If the sustainer doesn't light, I would suspect that the deployment of the booster parachute would pull it free. If not, you will have a chute at either end. Clairm had a flight were the sustainer didn't light and the whole stack came down with just the booster chute with no damage.* I don't know how to reference another post, search for 'Cosmodrome Aerobee Hi', post dated 12/01/2014.


* not recommended.

Too bad my staging timer doesn’t have dual event capability. I could use a small BP charge to pop the booster clear of the upper-stage a second or so before the sustainer motor is due to fire.

On the other hand; there just might be enough room in the lower electronics bay for two separate staging timers if they could operate off of a single 9v battery.

What 29mm CTI case has the same overall length as an AeroTech 180 case. I can’t fit anything longer in the upper stage.

I believe that is the 3 grain case. The 3 grain load I have fits perfectly in my 180 case.

boomtube-mk2 said:

What 29mm CTI case has the same overall length as an AeroTech 180 case. I can’t fit anything longer in the upper stage.

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Why can't you fit a longer case?

There is NO need to use a CTI motor in the sustainer. Sure they are easier to light but if your using a crazy Jim ignited then you all good. Those things are like mini fireworks it's crazy, they will light anything and everything! Stage with whatever motors/cases you have. Don't go out of your way to buy a new case when there is no reason to. Also I don't think there is a need to redip Jims igniter unless you're moving up to larger motors. Just my 2 cents 😃

I'm not a 2 stage HP veteran, but just attended a meeting where the presenter recommended taping a small diameter dowel to the igniter wires so that when the booster lights, the igniter in the sustainer won't buckle/collapse under the acceleration forces and end up at the bottom of your motor core. Food for thought.

conman13 said:

There is NO need to use a CTI motor in the sustainer. Sure they are easier to light but if your using a crazy Jim ignited then you all good. Those things are like mini fireworks it's crazy, they will light anything and everything! Stage with whatever motors/cases you have. Don't go out of your way to buy a new case when there is no reason to. Also I don't think there is a need to redip Jims igniter unless you're moving up to larger motors. Just my 2 cents ��

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Are you talking about his "e-matches"...the ones with the orange wires and purple pyrogen head with the little metal band? If so, these are e-matches and won't light "anything and everything". Those are designed for BP.

Now if you're talking about the ones he makes with yellow wires and the large grey pyrogen head then yes, they will likely light your motor BUT you would have to do some ground testing with electronics. I don't know the details on these things (although I have some), but it's highly unlikely that these are as low-current as an ematch, but are likely require less current than the average "starter"/"igniter".

And also I'm certainly not trying to shoot you down AT ALL. I just want to make it clear that a bare electric match is NOT ideal for motor ignition.

marcusSRG said:

Are you talking about his "e-matches"...the ones with the orange wires and purple pyrogen head with the little metal band? If so, these are e-matches and won't light "anything and everything". Those are designed for BP.

Now if you're talking about the ones he makes with yellow wires and the large grey pyrogen head then yes, they will likely light your motor BUT you would have to do some ground testing with electronics. I don't know the details on these things (although I have some), but it's highly unlikely that these are as low-current as an ematch, but are likely require less current than the average "starter"/"igniter".

And also I'm certainly not trying to shoot you down AT ALL. I just want to make it clear that a bare electric match is NOT ideal for motor ignition.

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They are the orange ones and I use them on all of my Loki 38mm loads and they light up perfect every time.

I'm glad you've had some repeated success with them. They definitely *can* work and I've seen them work, I just would never use them in a cluster/airstart situation without dipping them in a pyrogen. What propellants have you used them with?

And again, I'm not trying to rain on your parade at all... if you've got a great record with them then keep it up. I just wouldn't put my faith in one to light a second stage or especially a cluster. They're made to light bp...they "pop" rather than burn long and hot.

I will say that I think they work best in 29mm MPR/HPR motors with easy to light propellants--G80T, G125T for example. G38FJ if it would fit. The old smaller DaveyFire ematches (forgot their designation) fit G38FJs very well and would light them reliably. My guess is because these were about the smallest motors they would fit in, there's very little (to no) space between the grain and match head, and the propellant is easy to light.

The CJ matches burn longer than the MJG "regular" matches. Doesn't surprise me that they would light a small motor. For 38mm though, I would dip a match - no reason not to. I have been using the magnelite stuff (I get from PML) for many years. I believe the formula changed in the last year or so, and the texture of the stuff on the match is perfect (won't easily crack off).

Jim

Thanks for the clarification on burn time with those. I didn't realize they were MJG matches--thought they were a knock off. That I wasn't aware of, thanks.

marcusSRG said:

Thanks for the clarification on burn time with those. I didn't realize they were MJG matches--thought they were a knock off. That I wasn't aware of, thanks.

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I'm not sure I provided much of a clarification. I have, and can compare, the regulated MJG J-tek matches against CJ's matches (which are not MJG so far as I know). They burn quite differently. The J-tek matches pop whereas the CJ matches have a relatively long burn.

Jim

cosmodrome said:

Why can't you fit a longer case?

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Because the lower electronics bay that houses the staging timer prevents using any motor longer than the 29/180.

I thought about allowing enough room for a 240 case but that put the staging timer’s E-Bay farther up the airframe than I wanted it to be. In addition it would require even longer wire leads from the timer to the sustainer motor.

Still the Aerotech 29/180 will allow for the use of an H165R or even an H238T motors which when accompanied by the boosters 38/240 using an H148R or H242T should be enough power to be entertaining.

I “glassed” the inside of the inter-stage’s coupler last night and completed the fillets on the boosters fins, outside/inside/root.

I have one of the upper stage’s fins glued on but the weather outside while not precisely “Frightful” is dreary, drippy and wet so I can’t get the remaining two fins sanded. Takes a while with an electric sander to get the airfoils and I don’t do that indoors.

I have the access hole cut and the cover hatch built for the staging timer’s electronics bay and I’m waiting for some parts to complete said bay.

I’m also waiting for the parts to build the forward electronics bay that will hold the altimeter for recovery deployment. I wish I could think-up a means by which I could build this as dual-deploy but without cutting the airframe into sections a solution eludes me.

Some form of two barrel “shotgun” system might work but the complexity of that is more than I want to get into.

JimJarvis50 said:

I'm not sure I provided much of a clarification. I have, and can compare, the regulated MJG J-tek matches against CJ's matches (which are not MJG so far as I know). They burn quite differently. The J-tek matches pop whereas the CJ matches have a relatively long burn.

Jim

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Oh I read too quickly, sorry. I thought you said they WERE MJG matches. I was wondering why I didn't see one with an orange leadwire on their website! It's been so long since I've used another ematch I don't have anything to compare them to. I was using Q2s before this and had a 5 year period of not flying prior to that. I used Oxrals and Daveyfires back in the day.

Well the booster and inter-stage coupler are assembled sans the little detail bits along the bottom of the booster airframe.

The second stage is moving right along with all three fins installed, the lower electronics bay completed and the nosecone/payload bay with its electronics bay is 90%. Still have to shape and install the fin conduits.

The really sad part is I’ll get this rocket assembled and then it will likely sit of weeks before I get nice enough weather to take it outside to primer and paint. Then it will sit until at least April before I have the first opportunity to actually launch it.